Magnetically compensated cross field flowing gas laser

ABSTRACT

A flowing gas laser having an electric discharge plasma with the electric field oriented transversely with respect to the flow of gases therethrough is provided with a magnetic field which is oriented transversely with respect to both the flow and the electric field to overcome the forces of flowing gases thereon.

United States Patent [1 1 Pinsley et al.

[ Sept. 25, 1973 MAGNETICALLY COMPENSATED CROSS FIELD FLOWING GAS LASER[75} Inventors: Edward A. Pinsley, North Palm Beach, Fla; Albert W.Angelbeck, East Hartford; Carl J. Buczek, Manchester. both of Conn.

[73] Assignee: United Aircraft Corporation, East Hartford. Conn.

[22} Filed: Jan. 7, 1972 21 App]. No.: 216,302

Related U.S. Application Data [63] Continuation of Ser. No. 877,320,Nov. 17, 1969,

abandoned.

[52] US. Cl. 331/945, 330/4.3 [51] Int. Cl. [1018 3/22, HOls 3/09 [58]Field of Search 331/945; 330/43; 315/3971 fWWP JVP/ Z y [56] ReferencesCited UNITED STATES PATENTS 3.51 %,714 5/1970 Angelbeck 331/9453,577,096 5/l97l Bridges et al. 331/945 Primary E.mminerDavid SchonbergAssistant ExaminerR. J. Webster Altorney- Anthony J. Criso [57] ABSTRACTA flowing gas laser having an electric discharge plasma with theelectric field oriented transversely with respect to the flow of gasestherethrough is provided with a magnetic field which is orientedtransversely with respect to both the flow and the electric field toovercome the forces of flowing gases thereon.

2 Claims, 1 Drawing Figure MAGNETICALLY COMPENSATED CROSS FIELD FLOWINGGAS LASER This is a continuation of application Ser. No. 877,320, filedNov. 17, 1969 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention relatesto flowing gas lasers, and more particularly to means for compensatingthe flow field effects on the electric discharge plasma thereof.

2. Description of the Prior Art Recently, there has been a number ofadvances in the gas laser art. Particularly, it has become known thatmolecular, vibrational lasers of the flow-ing type are capable ofextremely high power density, specific power and total power output.These characteristics are further enhanced in a flowing gas laser inwhich the optical gain region (which may be an optical cavity in thecase of an oscillator, or one or more optical gain paths betweensuitable mirrors in the case of an amplifier) is coextensive with theelectric discharge plasma within which the population inversion of thelasing gas is achieved. 1f the plasma extends outside of are opticalgain region, the electrical efficiency and the total output powercapability are decreased. Heating of the gases by the plasma ismitigated when the gas flows across the least dimension thereof. Thus, alaser with the optical gain path and plasma coextensively transverse toflow has been found to be highly desirable.

A difficulty resides in overcoming the flow field effects which theflowing gas has upon the plasma, Specifically, the plasma tends to beblown downstream, and thus out of a narrow optical gain region, orspread in an inefficient fashion across a broad optical gain region. Toovercome this, compensation has been provided with RE pre-ionizationmeans in a copending application of the same assignee entitledTRANSVERSE GAS LASER, Ser. No. 857,647, filed on Sept. 10, I969, byBullis and Penney. In some instances, the RF pre-ionization solution isunattractive due to the need to provide an RF power supply, and theadditional weight and power consumption attendant therewith. There are,obviously, other situations in which RF preionization is not perfectlysuitable.

SUMMARY OF THE INVENTION The object of the present invention is toprovide im proved compensation for a transverse electric dischargeplasma in a flowing gas laser.

According to the present invention, a magnetic field is orientedtransversely with respect to both gas flow and the E field of across-field electric discharge flowing gas laser. The magnetic fieldexerts a force on the electrons drifting from the cathode to the anodeto create a force in the direction opposite to the flow of gases,thereby compensating for flow field effects which tend to blow theelectric discharge plasma downstream.

The present invention is capable of simple implementation, not requiringadditional power supplies or the power consumption and weight attendanttherewith. The present invention may be implemented simply withpermanent magnets, which are nonconsumptive.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent in the light of the followingdetailed description of a preferred embodiment thereof, as illustratedin the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE herein comprises asimplified. schematicized, partially broken away perspective view ofaflowing gas laser with magnetic flow field compensation in accordancewith the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURE, aflowing gas laser incorporating the present invention comprises aconduit 10 through which lasing and other gases flow from a source 12 ina direction indicated by an arrow 14. The gas mixture may typicallycomprise nearly equal parts of carbon dioxide, nitrogen and helium, orother ratios or mixtures known in the art. It is important to note thatthe particular gas mixture is not really significant to the presentinvention since the invention incorporates the force effect of amagnetic field on drifting electrons within an electric dischargeplasma, all of which is independent of the particular gas mixtureemployed; even though the electron drift depends in part on the gasmixture, the magnetic field may be adjusted according.

Appended to the conduit 10 are structures which include mirrors 15, 16to form an optical cavity, including suitable output coupling capability(such as a partially reflecting mirror or a hole 17 in one of themirrors), as well as the anode 18 and cathode 19 necessary to establishan electric discharge plasma. The anode 18 and cathode 19 are connectedby suitable electrical conductors 20 to a suitable power supply 22, allas is known in the art. Disposed above and below the region between thestructures 15-l9 are magnetic pole pieces 24, 26 respectively. Thesecreate a magnetic field from top to bottom as viewed in the FIGURE, andas indicated by the vector 28. The migration of electrons from thecathode to the anode result in a current vector (opposite to electronflow) in the direction from the anode 18 to the cathode 19 as shown bythe vector 30.

As is known, the interaction between the current and the magnetic fieldwill result in an upstream force as indicated by the force vector 32.This force is exerted upon the electrons, and tends to maintain theelectrons in an area between the anode and cathode. However, the flowfield effects on the ions are much greater than those on the electronssince the mass of the ions is several orders of magnitude greater thanthe mass of the electrons. But, electrical neutrality dictates that ifthe electrons are maintained in the area between the anode and cathode,as the ions tend to be blown downstream, there is an electrical force ofattraction between them which causes the ions to remain in the samegeneral vicinity with the electrons. Thus, the plasma established by theelectric field between the anode l8 and cathode 19 is maintained in anarea substantially between the pole pieces 24, 26.

The magnetic field may be created by electromagnets instead of thepermanent magnets 24, 26 if desired. The downstream end of the conduit10 may be connected to suitable exhaust means so as to vent the gases toambient, or suitable flow means may be provided so as to create aclosed-loop or closed cycle system in which the gases are recirculatedcontinuously through the conduit 10, as is known in the art. What isimportant to the present invention is that the magnetic field be capableof generating a force on the electrons as a result of the J-cross-Bproduct which is opposite to the flow of gases through the electricdischarge plasma.

'Typical parameters for a small, laboratory model of the presentinvention include a conduit having a width of six inches, a depth ofone-half inch, with a flow of gases therein having a mixture of 1:3:6 CON and He, respectively, at a total pressure of Torr and a flow velocityof M/sec. The magnetic pole pieces 24, 26 provided 300 gauss, and theelectric field comprised approximately 100-150 volts per centimeter.

Although the invention has been shown and described with respect to apreferred embodiment thereof, it should be understood by those skilledin the art that the foregoing and various other changes and omissions inthe form and detail thereof may be made therein without departing fromthe spirit and scope of the invention.

Having thus described a typical embodiment of our invention, that whichwe claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a flowing gas laser of the type in which electrical power iscoupled into the gas flowing through an optical gain region throughelectron collisions within an electric discharge plasma established inthe optical gain region, an optical output power is coupled from the op-4 tical gain region, the comprising comprising:

means for establishing an optical gain region which has an optical axistherethrough; means for providing a flow of a gas mixture including alasing gas through said optical gain region in a direction transversetothe axis; means for establishing an electric discharge plasma withinsaid optical gain region, the electric field of said plasma beingtransverse to the flow of gases through said optical gain region; andmeans for establishing a magnetic field in said optical gain region, theflux lines of the magnetic field being transverse with respect to bothsaid flow of gases and with respect to said electric field, and orientedin a direction to generate a force, on electrons in the plasma driftingfrom the cathode to the anode which is opposite to the direction of gasflow through said optical gain region for compensating for flow fieldeffects which tend to blow the electric discharge plasma downstream.

2. The gas laser according to claim 1 wherein the dimension of saidoptical gain region in the direction of said electric field is greaterthan the dimension of said optical gain region in the direction of saidmagnetic field.

w UNITED STATES EATENT oEEicE CERTIFICATE OF CORRECTION Patent No.3,761,836 S Dated September 25, 1973 Inventofls) EDWARD A. PINSLEY ET ALit is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

- Column 1, line 15, flo w-ing" should read flowing B line 24, "are"should read the line 3 7, I "RE" should read Column 4, linei l, de 1 etie"comprising' first occurrence I and ineert combination Signed andsealed this 25th day of Deoexrlbe 1973.

(SEAL) Attest':

EDWARD M. L TCEEE,JR. v v RENE D. TEGTMEYER Attesting Officer 7 ActingCommissioner of Patents zggg UNITED STATES PATENT @FFiCE QERHWCATE OF(IDRRECTEON Patent No. 3 761 ,836 v Dated September 25 1973 Inventofls)EDWARD A PINSLEY ET AL appears in the above-identified patent it iscertified that error ted as shown below:

and that said Letters Patent are hereby correc Column 1, line 15,"flow-ing" should read flowing line 24, "are" Should read the line 37,"RE" should read RF Column 4, line 1, delete "comprising" firstoccurrence and insert combination Signed and sealed this 25th day ofDecember 1973.

(SEAL) Attest':

RENE D.. TEGTMEYER Acting Commissioner of Patents EDWARD M.ELETCHER, JR.Attesting Officer

1. In a flowing gas laser of the type in which electrical power iscoupled into the gas flowing through an optical gain region throughelectron collisions within an electric discharge plasma established inthe optical gain region, an optical output power is coupled from theoptical gain region, the comprising comprising: means for establishingan optical gain region which has an optical axis therethrough; means forproviding a flow of a gas mixture including a lasing gas through saidoptical gain region in a direction transverse to the axis; means forestablishing an electric discharge plasma within said optical gainregion, the electric field of said plasma being transverse to the flowof gases through said optical gain region; and means for establishing amagnetic field in said optical gain region, the flux lines of themagnetic field being transverse with respect to both said flow of gasesand with respect to said electric field, and oriented in a direction togenerate a force, on electrons in the plasma drifting from the cathodeto the anode which is opposite to the direction of gas flow through saidoptical gain region for compensating for flow field effects which tendto blow the electric discharge plasma downstream.
 2. The gas laseraccording to claim 1 wherein the dimension of said optical gain regionin the direction of said electric field is greater than the dimension ofsaid optical gain region in the direction of said magnetic field.